Its not that they don't get counted. Its just that nobody relies on them as search engines have faded the power of links from them a long time ago.

As of today if a web 2.0 sites has a high authority then a link from it will still be useful. But ask yourself this question how many web 2.0 sites do you know who are really good?

Most sites who were using these web 2.0 sites have already moved to paid hostings (as they have got way cheaper). And the sites who are still using web 2.0 platform, if you look closely then you will see that they have been updated a long time ago.